Molybdenum benzophenone compounds



Patented June 18, 1963 of New York No Drawing. Filed lune 11, 1962, Ser.No. 2iil,254 t Claims. (Ci. 2dii429) This invention relates toorganometallic compounds and more particularly to the molybdenumcarboxyl ate compounds which are obtained from reacting molybdenumpentachloride with certain aromatic monocarboxylic acids. The inventionadditionally concerns the method of using such compounds to catalyze thepolymerization of ethylenically unsaturated monomers.

The primary object of this invention is to provide a novel family ofuseful molybdenum carboxylate chloride compounds.

Another important object is to provide a practicable method forsynthesizing and isolating molybdenum carboxylate chloride compounds.

A further object is to provide an organomolybdenum catalyst for use inthe polymerization of ethylenically unsaturated hydrocarbons.

The compounds which are encompassed by this invention are the molybdenumcarboxyl ate chlorides having the following formula:

u GOO Monoyolz in which is a l-5, R is a radical selected from the groupconsisting of alkyl radicals having 1-10 carbon atoms, halogensubstituted alkyl radicals having 1l0 carbon atoms, acyloxy radicalshaving l-lO carbon atoms, alkox-y radicals having l-lO carbon atoms, thenitro radical, the phenyl radical, halogen radicals and hydrogen, x isl3, y is -3, z is l-4 and n is l-3. The preferred compounds Within theabove general formula are those compounds represented by the formulawhen x is 2, y is 0, n is 1 and z is 3, that is the molybdenumtrichloride dibenzoates having the formula:

in which R is a radical selected from the group consisting of alkylradicals having 1-10 carbon atoms, halogen substituted alkyl radicalshaving l-lO carbon atoms, acyloxy radicals having 1-lO carbon atoms,alkoxy radicals having 1-10 carbon atoms, the nitro radical, the phenylradical, halide radicals and hydrogen.

In the above formulas the attachment lines between the R group and theCO0 group and the benzene ring are shown between the normal positions onthe ring, and are intended to indicate that these groups can occupy anyof the available positions on the ring.

In accordance with this invention it has been found that molybdenumpentachloride is specifically reactive with benzene monocarboxylic acidsand substituted benzene monocarboxylic acids and capable of producingthe compounds encompassed by the above general formula when the reactionis effected in a non-polar solvent or a solvent substantially free ofactive hydrogen. In such a solvent the admixture of molybdenumpent-achloride and the selected benzene monocarboxylic acid react, Withagitation, at temperatures from room temperature up to a tempenatureapproaching the decomposition temperature of molybdenum trichloridedibenzoate, namely 210 C. to 220 C. to form the molybdenum benzenecarboxylate chlorides of this invention. The rate of reaction isundesirably low at room temperature and it is preferred that thereaction be carried out at a temperature above about 60 C.

The benzene monooarbox-ylic acids which are reactive with molybdenumpentachloride under the conditions 'above given include benzoic acid andbenzoic acids substituted on the ring with 1-5 alkyl radicals havingl-lO carbon atoms, 1-5 halogen-substituted alkyl radicals having 1-10carbon atoms, 1-5 alkoxy or acyloxy radicals having 1-10 carbon atoms,1-5 nitro radicals, 1-5 phenyl radicals, 1-5 halogen radicals andhydrogen. In all cases, the lower carbon chain length substituents, forexample, 1-4 carbon atoms, represent more important and commerciallyavailable reactant acids and for these reasons constitute a preferredgroup.

The halogen subst-ituent on the ring or in the halogensubstituted alkylradicals is preferably chlorine, and when R is a halogen, a ispreferably 1-3. When R is phenyl, a is preferably 1. Examples ofspecific acids which are representative of the above groups and whichrepresent preferred reactants include methyl benzoic acid, ethyl benzoicacid, pentamethyl benzoic acid, nitro benzoic acid, chloro-methylbenzoic acid, chloro-benzoic acid, 2,5 dichloro-benzoic acid,benzotrichloride, fiuoro-benzoic acid, p-rnethoxy benzoic acid, ethoxybenzoic acid, trimethoxy benzoic acid, acetyl salicylic acid,nitro-benzoic acid, etc.

The reaction is satisfactorily effected in non-polar solvents orsolvents which do not contain an active hydrogen and which are onlypartial solvents for, and pref era-bly non-solvents for, the compoundsof this invention. Available solvents which meet these requirementsinclude carbon tetrachloride, benzene, nitrobenzene, toluene, n-hexane,ethylene dichloride, and perchloroethane, and of this group benzene,carbon tetrachloride and nitrobenzene constitute a preferred sub-group.

The molybdenum chloride benzoates of this invention are formed byadmixing and thereafter agitating molybdenum pentachloride :and theselected benzoic acid, in one of the above described solvents, forexample benzene, preferably raising the temperature to about 60 C. andmaintaining this or a higher temperature for a time sufficient to formthe desired compound and thereafter separating the compound from thereacting medium. The time which is required has been found to vary fromabout 3 to 4 hours at the reflux temperature of benzene to form themolybdenum trichloride dibenzoates up to about 120 hours, or longer, toform dimolybdenum dioxychloride tribenzoate.

Two of the chlorine atoms of molybdenum pentachloride are relativelyeasily replaced with the carboxylate radical. All that is necessary toeffect this reaction is to provide the stoichiometric proportions of 2mols of benzoic acid to 1 mol of molybdenum pentachloride and uponagitation, preferably above 60 C. the reaction begins to occur.Increasing the time of the reaction under these conditions, merelyincreases the yield. In order to remove others of the remaining threechlorine atoms of the molybdenum pentachloride it [is necessary tosubstantially extend the reaction time and it is advantageous toincrease the temperature appreciably above 60 C. an to carry out thereaction in the presence of an excess of the selected benzoic acidreactant. A convenient method for accomplishing this result is to selecta solvent having a relatively high refluxing temperature but preferablyappreciably below the decomposition temperature of the compounds of thisinvention, namely 210 C.220 C., for example, a reflux temperature in therange of C.- C. Under such conditions a total of four of the chlorineatoms of the molybdenum pentachloride can be replaced and the latter twochlorines are replaced with oxygen or another carboxylate group.Although the rethe compounds of this invention are less bright and haveI a lighter green color. In the presence of excess benzoic acidreactant, the initial compound of this invention which if formed ismolybdenum trichloride dibenzoate and as refluxing is continued, acondensation or partial polymerization of the dibenzoate occurs, andpossibly simultaneously with the formation of molybdenum dichloridetribenzzoate, to ultimately form dimolybdenurn dioxychloridetribenzoate. When the quantity of the benzoic acid reactant which ispresent is less than mols of benzoic acid to 1 mol of molybdenumpentachloride or the reaction time is too short, a compound is formedcontaining less chlorine and more oxygen, or less chlorine and morebenzoate, or less chlorine and more oxygen and more benzoate than ispresent in molybdenum trichloride dibenzoate, but intermediate to theamounts of chlorine, oxygen and benzoate which are present indimolybdenum dioxychloride tribenzoate. Moreover a series of suchcompounds are formed and each such intermediate compound functional-1yserves as a starting material which with additional benzoic acidreactant corresponding to that used in its formation and additionalreaction time will form dimolybdenum dioxychloride tribenzoate.

When the proportion of benzoic acid reactant to molybdenumpenrtachloride is 1 to 1, in benzene, molybdenum monobenzoatetetrachloride is formed and upon continued reaction a condensationoccurs to produce molybdenum oxytrichloride benzophenone and thiscondensation mechanism is comparable to a Friedel-Crafts condensation.Using a 1 to 1 proportion of benzoic acid to molybdenum pentachloride intoluene and refluxing for 17 hours produced molybdenum oxy-trichloride4- methyl benzophenone. In the presence of more than 2 mols of thebenzoic acid reactant for each mol of molybdenum pentachloride thebenzophenone condensation does not occur, and the product is entirelymolybdenum rtrichloride dibenzoate or is an admixture of molybdenumtrichloride dibenzoate and one or more of the above mentionedintermediates, or entirely one of the intermediates depending upon thereaction time and temperature and the degree of excess concentration ofthe benzoic acid reactant.

The compounds of this invention are all green crystalline solids, andalthough the shade of green varies slightly it is most aptly describedas a light green. The compounds can be separated from the reactingmedium by filtration using conventional techniques, for example, byvacuum filtration through a sintered glass filter tube. All of thecompounds except the dimolybdenum dioxych'loride tribenzoate hydrolyzein the presence of moisture and for this reason the filtration step ispreferably performed in a dry atmosphere. The hygroscopicity of thecompounds of this invention appears to decrease as the condensation orpolymerization increases, for example, molybdenum trichloride dibenzoateand molybdenum oxytrichloride benzophenone are immediately hydrolyzedwith water whereas the intermediate condensation compound resulting fromrefluxing 3 mols of benzoic acid and 1 mol of molybdenum pentachloridein benzene for 5 days hydrolyzes in water more slowly and dimoflybdenumdioxychloride tribenzoate is not hydrolyzed to any discernible extent.The compounds of this invention react with alcohols to give thecorresponding ester, and undergo a condensation comparable to a Friedel-Crafts condensation to yield the corresponding ketone. The compoundshave been found to be useful as catalysts in the polymerization ofethylenically unsaturated hydrocarbons, for example, styrene. They areailso use ful as co-cat-alysts in the low pressure polymerization ofethylene and propylene, such co-catalysts being the alkyl metalcompounds of groups 1A, 2A and 3A of the periodic table and specificallyincluding alkyl compounds of lithium, magnesium, caicium, boron andaluminum.

The examples which follow illustrate in greater detail typicallysuitable operating conditions, proportions of reactants and proceduresfor separating the compounds of this invention as well as productcharacteristics, but it is to be understood that they are illustrativeonly and do not contam the defining limits of this invention which havebeen given hereinabove. All experiments were conducted under a drynitrogen atmosphere and all material transferals were accomplished in adry box.

Example I 33.7 grams of benzoic acid was admixed with 500 ml. of carbontetrachloride and 37.5 grams of molybdenum pentachloride was addedthereto, with stirring for a 10 minute period. A green solid wasimmediately formed with no noticeable heat generation. The reactionmixture was then refluxed for 16 hours and hydrogen chloride wascontinuously evolved. After cooling to room temperature, a finelycrystalline solid was separated by vacuum filtration through a sinteredglass filter tube. The separated solid was vacuum dried overnight atroom temperature to obtain 57.2 grams of a light green solid, thusgiving a yield of 93.3%. A melting point determination was made and themelting point of 210 C.-220 C. was established and hydrogen chloride wasevolved at the melting temperature. Upon exposure to the atmosphere, theproduct turned brown, and the pungent odor of benzoyl chloride wasapparent. The so lid product was found to be more than 2% (soluble inacetone and ethanol to give dark brown solutions.

The product is insoluble in water and immediately hydrolyzes to benzoicacid. The product is soluble in an ethanol-Water solvent pair. It isalso more than 2% soluble in ethyl acetate to produce dark-greensolutions. The product is only slightly soluble in diethyl ether to givea light green solution, and is completely insoluble in carbon disulfide,carbon tetrachloride and petroleum ether. When the product is refluxedin benzene, at room temperature for an extended period benzophenone isproduced.

A proportion of the product was analyzed and found to contain 37.03%carbon, 2.30% hydrogen, 23.8% chlorine and 20.8% molybdenum, and thisanalysis corresponds to a compound having the formula C H C'l MoO withinthe limits of analytical error.

Styrene monomer, inhibited to resist polymerization at normal roomtemperature, was slowly added to a container containing a portion of themolybdenum trichloride dibenzoate product, prepared above, until themolybdenum trichloride dibenzoate represented 1.1% by Weight of thetotal reaction mixture, and the mass was agitated for 30 minutes andthereafter allowed to stand for 20 hours at 20 C.24 C. At the end ofthis period the polymerization mixtures were extracted with hot tolueneand precipitated with excess methanol to obtain the higher molecularWeight fraction. The precipitated polymers were then separated byfiltration through fritted glass, Gooch-type crucibles. The separatedpolymer was then vacuum dried to constant weight, first at roomtemperature and thereafter in an oven at 60 C. and 10 mm. of mercurypressure. The precipitated polymer was in the form of a viscous mass andrepresented a 37.8% yield based on the original styrene monomer weight.The softening point of the polymer was determined to be 77 C.78 C. andthe melting range was found to be C.- C.

Example 11 104 grams of benzoic acid was admixed in 500 ml.

of benzene with 46.5 grams of molybdenum pentachloride, with stirring,over a 25 minute period without which is the equivalent of (C H COO) MoO Cl.

rise in the reaction temperature. The reaction mixture was refluxed for5 days and at the end of this time there was no further detectableevolution of hydrogen chloride. A light green crystalline product wasseparated by filtration in air. No benzoyl chloride was detected in thereaction mixture filtrate by vacuum distillation. The reaction mixturefiltrate was found to consist entirely of benzoic acid and to be freefrom benzophenone. The crystalline product was washed successively withbenzene, diethyl ether, methanol and Water and there was no observablereaction with any of these solvents. The product was then dried bysuccessive methanol and ether washings and 56 grams of product wererecovered, representing 100% yield.

A proportion of the product was analyzed and found to contain 39.50%carbon, 2.40% hydrogen, 5.70% chlorine and 29.77% molybdenum and thisanalysis corresponds to a composition having a formula The greencrystalline product is completely non-hydroscopic and resists attack bynitric and hydrochloric acids. The product is completely soluble inaqueous sulfuric acid at a concentration greater than 79% by weight torelease benzoic acid. The product required refluxing for several hourswith aqueous sodium hydroxide in order to effect saponification. Theproduct is insoluble in common organic solvents except chloroform andpyridine with which it reacts to replace benzoate. The product thermallydecomposes above 300 C. without melting.

A mixture of 10 grams of the product and 50 ml. of pyridine was refluxedfor 1 /2 hours. The reaction mixture was vacuum evaporated and theresidue was treated with aqueous hydrochloric acid to remove unreactedpyridine. An orange-brown solid product was formed and was washedsuccessively with water, methanol and diethyl ether and 2.34 grams ofbenzoic acid was isolated from the combined organic extracts. Theproduct was then extracted in a Soxhlet apparatus to obtain a smallamount of yellow-orange solid. A proportion of the yellow-orange wasanalyzed and found to contain 37.53% carbon, 2.62% hydrogen, 32.13%molybdenum and 2.25% nitrogen, and this analysis corresponds to acompound having the formula (C H COO) Mo O (C I-I N), within the normallimits of analytical error. The product was slightly soluble inchloroform but was insoluble in Water and ethanol.

Example 111 A mixture of 6.85 grams of molybdenum trichloridedibenzoate, prepared as in Example I, and 5.73 grams of benzoic acid in50 ml. of benzene was refluxed for 5 days. At the end of 5 days a greencrystalline product was separated by filtration in air. The reactionmixture filtrate was vacuum distilled and no benzoyl chloride orbenzophenone was detected. The green crystalline solid was treated withwater and no hydrolysis occurred. It was washed successively withmethanol and diethyl ether and further dried by infrared lamp heat toobtain 4.62 grams of product. A proportion of the product was analyzedand found to contain 39.88% carbon, 2.43% hydrogen, 5.63% chlorine and30.2% molybdenum, and this analysis corresponds to a compound having theformula C H ClMo O within the normal limits of analytical error.

The infrared spectrum and X-ray diffraction pattern of the product wastaken and found to be identical with the infrared spectrum and X-raydiffraction pattern of the product which was prepared in Example II.

Example IV 21.9 grams of benzoic acid was dissolved in 500 ml. ofbenzene and 48.75 grams of molybdenum pentachloride was added thereto,with stirring, over an 8 minute period. The reaction mixture wasrefluxed for 5 days without cessation of hydrogen chloride evolution.The reaction mixture was concentrated by distillation of 300 ml.benzene, and hydrogen chloride was noted to be evolved during thisdistillation. The reaction mixture was refluxed for an additional 8hours and hydrogen chloride Was still evolving. The refluxing wasstopped and the mixture cooled to room temperature and thereafterbriefly refrigerated. A finely crystalline, light green solid wasseparated from the reaction mixture by filtration and washed withbenzene. It was noted that the product had an appreciable benzenesolubility. The separated product was vacuum dried and 50.6 grams wereisolated, giving a 70% yield.

A portion of the product was analyzed and found to contain 38.09%carbon, 2.52% hydrogen, 26.42% chlorine and 24.03% molybdenum, and thisanalysis corresponds to a compound having the formula CmHmClsMOOz withinthe normal limits of analytical error.

A portion of the product was treated with water and immediate hydrolysisoccurred yielding benzophenone. A portion of the benzophenone wasisolated and the boiling point was found to be 108 C.109 C.

Styrene monomer, inhibited to resist polymerization at normal roomtemperature, was slowly added to a container containing a portion of themolybdenum oxytrichloride benzophenone product, prepared above, untilthe molybdenum dibenzoate trichloride benzophenone represented 1.35% byWeight of the total reaction mixture, and the mass was agitated for 30minutes and thereafter allowed to stand for 20 hours at 20 C.24 C. Atthe end of this period the polymerization mixtures were extracted withhot toluene and precipitated with excess methanol to obtain the highermolecular Weight fraction. The precipitated polymers were then separatedby filtration through fritted glass, Gooch-type crucibles. The separatedpolymer was then vacuum dried to constant weight, first at roomtemperature and thereafter in an oven at 60 C. and 10 mm. of mercurypressure. The precipitated polymer was in the form of a viscous mass andrepresented a 32.4% yield based on the original styrene monomer weight.The melting range of the polyrner was found to be 60 C.70 C.

Example V 22.7 grams of benzoic acid was admixed with 500 ml. of tolueneand to this mixture 50.8 grams of molybdenum pentachloride Was added,with stirring, over an 8 minute period. A slight exothermic reactionoccurred giving a brown solution and considerable evolution of hydrogenchloride. The reaction mixture was refluxed for 17 hours to form a finecrystalline solid, which was molybdenum oxytrichloride4-methylbenzop-henone. The crystalline solid was stirred into 500 ml. of10% hydrochloric acid and formed a gelatinous, inorganic hydrolysisproduct which was difiicult to separate by filtration. The aqueous acidlayer was saturated with ammonium chloride, which increased thefiltration rate and the aqueous layer Was separated and extracted withether. The combined ether extract and toluene solution was washed withwater, treated wih Drierite, and distilled to strip off the organicsolvents. The pot residue was dissolved in ether, and this solution wasextracted with 10% aqueous sodium hydroxide. From this alkali extract,after acidification, 0.3 gram of benzoic acid was obtained. Thenon-alkali extracted organic product was fractiona-lly distilled througha Vigreaux column yielding only one fraction and 26 grams of product wasrecovered. The boiling point of the fraction was found to be 103 C. C.,and the melting point was 55 C.57 C. The product was identified as4-methylbenzophenone, by its 2,4-dinitrophenylhydrazone, melting pointof 200 C.201 C.

Example VI 7.93 grams of molybdenum trichloride dibenzoate was ExampleVII 60 grams of benzoic acid was admixed with 500 ml. of benzene and44.7 grams of molybdenum pentachloride was quickly added, with stirring.There was rapid formation of a bright green solid. The reaction mixturewas refluxed for days. The solid reaction product was separated byvacuum filtration through a fritted-glass filter tube. After washingwith benzene, the solid was. vacuum dried at room temperature to obtain63.3 grams darkgreen, crystalline solid. Upon exposure to air, theproduct slowly turned brown and evolved hydrogen chloride. Some minutesexposure to water was required for appreciable hydrolysis. A portion ofthe product was analyzed and found to contain 38.15% carbon, 2.32%hydrogen, 20.4% chlorine and 23.14% molybdenum, and this analysiscorresponds to a compound having the formula (C H COO) MoO Cl Thecompound had a melting point of 220 C.-221 C. and at this temperaturethe evolution of hydrogen chloride was evident.

This application is a division of copending application Serial No.803,590, filed April 2, 1959, now Patent No. 3,042,694.

What is claimed is:

1. Molybdenum oxytrichloride benzophenone.

2. Molybdenum oxytrichloride 4-methylbenzophenone.

3. A method for making molybdenum oxytrichloride benzophenone whichcomprises the step of refluxing molybdenum pentachloride and benzoicacid in benzene, said molybdenum pentachloride and said benzoic acidbeing present in a molar ratio of about 1:1 and continuing saidrefluxing until said compound is formed.

4. A method for forming molybdenum oxytrichloride 4-methylbenzophenonewhich comprises the step of refluxing molybdenum pentachloride andbenzoic acid in toluene, said molybdenum pentachloride and said benzoicacid being present in about a 1:1 molar ratio and continuing saidrefluxing until said compound is formed.

No references cited.

1. MOLYBDENUM OXYTRICHLORIDE BENZOPHENONE.